The soon to be obsolete Space Shuttle was supposed to be reusable, but in fact major components, especially the rocket motors, had to be rebuilt essentially from scratch. Here are three possible ways to reduce costs to low Earth orbit that might be used either singly or in combination.

1. A truly reusable spacecraft with single-use rocket motors and a real ability to fly once a week. This seems plausible, maybe. The problems are reliability, reusability, and cost. The Space Shuttle certainly did NOT achieve the desired turn-around time or low cost.

2. Lower cost expendable booster that uses air-breathing solid fuel boosters for increased specific impulse. The way this would work would be that the exhaust of the solid fuel rocket would go into a ramjet sleeve. The fuel would be fuel-rich and hence oxygen-poor and would get most of its oxygen from the air. Of course, such a booster would need to maintain fairly low altitude in order to get sufficient oxygen in order function, resulting in increasing friction. The nice thing about the use of a solid fuel rocket in this case would be that there would never be any trouble about maintaining ignition. The fuel would already be burning when it mixed with the air. Such a booster would be smaller and hence cheaper than current all-rocket boosters.

3. Clearly, a vehicle that incorporated both of the above concepts might also cut costs further.